Conventionally, therapeutic treatment of a brain region has been performed by the so-called craniotomy, in which the cranial bones covering an outer peripheral portion of the brain are incised over a large extent. The craniotomy imposes a heavy burden on the patient, and recovery after the operation takes a long period of time. In view of this, there is a keen demand for a process for performing a brain region treatment without needing large craniotomy.
As means for administering a therapeutic substance such as medicinal liquids, neurotrophic factors, information transmission substances, genes and cells into a diseased part in the brain region, a method of inserting a medical device such as catheter into the brain region is contemplated.
For maintaining the efficacy of a therapeutic substance over a long period of time, on the other hand, slow or sustained release of the therapeutic substance to the diseased part is desired. In order to administer a therapeutic substance through a catheter inserted in a brain region over a long period of time, it is necessary to keep the catheter in the inserted state in the cranial bone for a rather long period of time. This imposes a significant influence on the patient, and is unfavorable from the viewpoint of sanitary control.
If a bag member or the like from which a therapeutic substance is released slowly or sustainedly can be indwelled at a predetermined position in a brain region, it would be possible to perform an effective treatment while alleviating the burden on the patient.
Japanese Application Publication No. 2004-535257 proposes a catheterization apparatus in which the distal end of the apparatus is provided with an implant device capable of being released into an internal body cavity of a patient.
The use of this catheterization apparatus ensures that an implant device filled with a therapeutic substance or the like can be indwelled in a patient's body.
On the other hand, in a brain region, the internal pressure is raised by the so-called brain pressure. When the implant device as described in Japanese Application Publication No. 2004-535257 is placed outside the catheter, therefore, the implant device may be compressed under the pressure from the brain tissues, during the period until the catheter is inserted to the diseased part. This may lead to such a problem as flow-out of the therapeutic substance contained in the implant device. Consequently, it becomes impossible to administer a sufficient amount of the therapeutic substance to the predetermined diseased part.
In recent years, there is a trend toward the use of capsules which envelope a therapeutic substance. This trend is from the viewpoint of handleability and sustained release in the body. If a catheter is inserted into a brain region in the condition where capsules are contained in the implant part as described in Japanese Application Publication No. 2004-535257, friction and collisions between the capsules would be generated during movement of the catheter, resulting in breakage of the capsules. Consequently, the therapeutic substance would flow out before the arrival of the catheter at the diseased part, and it would be impossible to administer a sufficient amount of the therapeutic substance to the predetermined diseased part.